Backfire

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Dec 30, 2017 | 02:01 AM

MikieG1971

Thread Starter

Instructor

Joined: Aug 2017

Posts: 246

Likes: 6

Backfire

I have noticed that when i suddenly jump into the rpm's i get some backfire activity. This is more prevalent if i am in a gear too high and step on it. When this happens, at the moment you hear the low pitch pop sounds, there is a cut in power and acceleration.
What should i be looking at on this 96 LT4?

Dec 30, 2017 | 11:19 AM

Red 91

Racer

Joined: May 2008

Posts: 312

Likes: 19

Its lean at throttle tip in, check fuel pressure with and without vac. Good luck

Dec 30, 2017 | 11:22 AM

MikieG1971

Thread Starter

Instructor

Joined: Aug 2017

Posts: 246

Likes: 6

I wondered if fuel octane grade could do this. Like mid or low grade might do this. Its not a knock. Just a low pitched pop.

Dec 30, 2017 | 02:05 PM

c4cruiser

Team Owner

Joined: Dec 1999

Posts: 34,873

Likes: 487

From: Lacey WA RVN 68-69

NCM Sinkhole Donor

Had a similar thing happen with my '93 autocross car (383, cam, headers, tune, etc)

It would run fine at speeds around 40-50, then it would misfire, get backfire out of the right side tail pipe, and start to run very bad. I have always run 92 octane premium.

Took it to my shop and they found a bad O2 sensor and a broken spark plug. They replaced both and the car is running great again. It did take a little time using diagnostic software tools to find the problems.

Dec 30, 2017 | 07:48 PM

FrankieD

Burning Brakes

Joined: Mar 2005

Posts: 1,083

Likes: 116

From: Richmond Hill Ontario

fouled spark plugs would cause that

Dec 31, 2017 | 12:21 AM

MikieG1971

Thread Starter

Instructor

Joined: Aug 2017

Posts: 246

Likes: 6

Happens when i really roll the power on in 1st or when i am cruising low rpm in say 4th ans decide to really push that gear. Before the real roar comes on sometines there is a "bloop" sound from under the hood. At that moment it feels like the car hit a wall. Its like the massive acceleration and power litterally cut out, then, bang....its back and we finish the gear.
It happens very fast!!

Dec 31, 2017 | 07:36 PM

93Rubie

Safety Car

Joined: Sep 2010

Posts: 3,752

Likes: 190

From: Indiana PA

Check the fuel pressure, also ignition issues could be a cause as well.

A scan tool will allow viewing of various sensors to determine if they are working properly and give feedback via the data if you know what your looking at.